This invention relates to a continuous process for drawing, crimping and collecting a tow composed of continuous filaments. More particularly, it relates to control of the crimping step during the start up of the continuous process.
In the commercial production of acrylic and other synthetic crimped fibers, a tow consisting of a multiplicity of spun continuous filaments is usually prepared first. The tow is then drawn, crimped in a stuffer box crimper and collected in a container. In the case of acrylic tow, the drawing is a wash-draw process as described by Davis and Palmer in U.S. Pat. No. 3,124,631 and the tow is moist when it is crimped and collected. In the operation of the stuffer box crimper, feed rolls force the tow being fed from the draw machine into a crimper chamber having its exit end restricted by an air cylinder loaded clapper plate, after which the crimped tow passes out of the crimper onto a cooling conveyor and is then piddled into a container. At start up, the tow is nonuniform and the piddler is set to divert it to waste collection. When the process is running smoothly, the piddler setting is changed to deliver the tow to the product collection container.
At each start up, the operator must continually adjust the clapper plate pressure of the crimper as the draw machine speed increases to operating speed, while also adjusting the supply of steam to the crimper. If the clapper plate pressure or steam pressure are adjusted incorrectly, the tow jams in the crimper and the draw machine must be shut down and restarted. In actual practice, the operator must try to get the "feel" of the crimper adjustments during start up, much as the operator of an automobile with manual transmission does; at times he fails and the crimper jams. To avoid undue waste as a consequence of operator error which may result in several false starts before the process is running smoothly, it is highly desirable to remove the human element from this portion of the start up of the process.